Association between preoperative blood–brain barrier dysfunction and postoperative delirium in older patients undergoing cardiac surgery: a prospective cohort study

Background Previous research indicates that the breakdown of the blood-brain barrier (BBB) is an early biomarker of cognitive dysfunction in humans, and it deteriorates with age. Patients with coronary heart disease may have concomitant impairment of the BBB. The off-pump coronary artery bypass grafting (OPCABG) is an effective surgical strategy for myocardial revascularization. However, cardiac surgery leads to a high incidence of postoperative delirium (POD), which can seriously affect clinical recovery. Therefore, it is important to explore whether preoperative BBB dysfunction is associated with POD in older patients undergoing OPCABG. Methods A prospective observational study was performed on OPCABG patients. Fifty older patients with coronary heart disease were recruited. Before surgery, patients underwent Gadolinium-enhanced magnetic resonance imaging. BBB was assessed using GE AW4.7 workstation GEN IQ module. The physiological parameter volume transfer constant (K_trans) is the most common and classical method for assessing BBB in the neuroimaging. All patients underwent standardized anesthetic management. Participants were assessed for POD twice daily for 5 days using the 3-Minute Diagnostic Confusion Assessment Method (3D-CAM) in non-intubated patients or the CAM for the Intensive Care Unit in intubated patients. Results 19 patients (38%) were diagnosed with POD. The preoperative median hippocampus K_trans of the POD and NPOD patients were 5.36 (IQR, 3.99,8.39) ×10^-3min^-1, and 3.89 (IQR, 3.40,4.68) ×10^-3min^-1. The preoperative median thalamus K_trans of the POD and NPOD patients were 4.80 (IQR, 3.60,6.62) ×10^-3min^-1, and 3.55 (IQR, 3.05,4.57) ×10^-3min^-1. Hippocampal and thalamic K_trans were statistically higher in the POD group compared to the NPOD group (P = 0.012 and P = 0.017). Univariable logistic regression analysis revealed that higher hippocampus K_trans (OR, 1.350; 95%CI, 1.048–1.740; P = 0.020) and thalamus K_trans (OR, 1.466; 95%CI, 1.017–2.113; P = 0.040) were significantly associated with higher odds of POD. Multivariable logistic regression analysis, adjustment variables were age, interleukin-6. The adjusted models revealed that preoperative hippocampus K_trans (OR, 1.250; 95%CI, 0.859–1.817; P = 0.244) and thalamus K_trans (OR, 1.164; 95% CI, 0.648–2.090; P = 0.611) were not associated with higher odds of POD. Conclusion POD patients have higher preoperative hippocampal and thalamic BBB permeability, but this was not an independent risk factor for POD.